Orthopedic Implant System

ABSTRACT

A surgical instrument configured to introduce a spinal fixation rod into a vertebral implant. When the spinal fixation rod is engaged with the surgical instrument and the surgical instrument is put into a retention configuration, the spinal fixation rod cannot be removed from the surgical instrument until the spinal fixation rod is properly oriented with respect to the surgical construct and the surgical instrument is released from the retention configuration. The surgical instrument includes a surgical instrument body, an actuator, an engagement assembly, and a transfer assembly that extends between the actuator and the engagement assembly. The surgical instrument can also be used as part of a method for introducing a spinal fixation rod or part of a kit for introducing a spinal fixation rod.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of pending U.S. application Ser. No.13/195,962 filed Aug. 2, 2011 which claims priority to, and the benefitof, U.S. Provisional Application No. 61/369,884 filed on Aug. 2, 2010.The contents of each application listed in this paragraph are herebyincorporated by reference in their entirety into this application.

TECHNICAL FIELD

The present disclosure relates generally to orthopedics, and inparticular relates to an implant system configured to implant a spinalfixation rod.

BACKGROUND

Spinal fusion is a surgical procedure used to join two or morevertebrae. The procedure is primarily used to eliminate pain, which canbe caused by a number of conditions, such as degenerative disc disease,vertebral fracture, spondylolisthesis and other diseases that causeinstability of the spine.

In most spinal fusion procedures, spinal fixation rods are attached tovertebral implants, which are first secured to adjacent vertebrae. Thevertebral implants generally include a bone anchor seat, a colletdisposed inside the anchor seat, and a bone anchor with a head portionattached to the collet. The spinal fixation rod is inserted through thecollet and fixed in place by a locking cap that attaches to the collet.

The placement of a spinal fixation rod within a vertebral implanttypically required a large opening in a patient's body to provide asurgeon with the visibility required at the surgical site. Recently,minimally invasive surgeries have become more common and desirable asthey reduce complications during surgery and recovery time aftersurgery. Minimally invasive spinal fusion surgery presents a number ofunique challenges including: retention of the spinal fixation rod withinthe surgical instrument during the insertion process; manipulation ofthe spinal fixation rod while it is inside the patient; and properalignment and positioning of the spinal fixation rod relative to thevertebral implants.

SUMMARY

In accordance with one embodiment, a surgical instrument is configuredto introduce a spinal fixation rod into, for instance, a series ofpedicle screws. The surgical instrument includes a gripping portion, ahousing member attached to the gripping member and defining an innerbore, a shaft positioned within the inner bore, an engagement tipattached to the housing member opposite the gripping portion anddefining a second inner bore, and an inner core positioned within thesecond inner bore.

In accordance with another embodiment, a surgical kit includes asurgical instrument configured to introduce a spinal fixation rod, and aplurality of spinal fixation rods. The fixation rods can have differentsizes and shapes.

In accordance with one embodiment, a surgical instrument includes anengagement assembly, a transfer assembly, and an actuator. Theengagement assembly includes a motion inhibitor configured to releasablyengage the spinal fixation rod and an engagement pocket defining a rodreceiving gap configured and sized to receive a portion of a spinalfixation rod and to permit the spinal fixation rod to pivot therein. Thetransfer assembly includes a shaft operably coupled to the motioninhibitor. The actuator is operably coupled to the shaft so as totranslate the shaft upon actuation of the actuator. The movement of theshaft causes at least one of the first and second engagement walls tomove toward the other of the first and second engagement walls between afirst position in which the rod receiving gap has a first size and asecond position in which the rod receiving gap has a second size. Thesecond size is less than the first size.

In one embodiment, the motion inhibitor is movable upon translation ofthe shaft to a third position in which the rod receiving gap has a thirdsize, the third size being less than the second size.

In yet another embodiment, the engagement pocket includes a lip, acurved lower surface extending from lip, and laterally opposed first andsecond retaining walls spaced apart from each other. Each of the firstand second retaining walls includes a bottom surface that is separatedfrom the lower surface so as to define a retention gap therebetween. Theretention gap is shaped and sized to receive a pair of engagement railsdisposed on opposite sides of the end portion of the spinal fixation rodof the spinal fixation rod. The motion inhibitor includes the secondengagement wall at a distal end thereof.

In one embodiment, the engagement assembly defines an ejection port incommunication with the rod receiving gap. The ejection port faces adirection substantially perpendicular to a longitudinal axis definedalong a length of the surgical instrument. The engagement assemblyincludes at least one retaining wall and a lip extending substantiallyperpendicular to the longitudinal axis defined along the length of thesurgical instrument at the ejection port. The engagement assemblyincludes at least one retaining wall and a lip extending substantiallyperpendicular to the longitudinal axis defined along the length of thesurgical instrument at the ejection port. The engagement pocket iscontoured and sized to allow removal of the spinal fixation rodtherefrom only when the spinal fixation rod is substantiallyperpendicular to the longitudinal axis defined by the surgicalinstrument body and when the motion inhibitor is in the first position.The motion inhibitor includes an auxiliary shaft having first and secondends. The auxiliary shaft includes a curved brake surface at the secondend thereof. The curved brake surface is configured to contact thespinal fixation rod. The curved brake surface has a substantiallyconcave configuration. The curved brake surface of the motion inhibitoris configured to receive a curve brake surface of the spinal fixationrod. The surgical instrument further includes a surgical instrument bodydefining a longitudinal axis and connected to the actuator and theengagement assembly. The surgical instrument body defines an inner boreextending along the longitudinal axis. The inner bore being is anddimensioned to slidably receive the shaft. The engagement assemblydefines a transverse bore configured and dimensioned to slidably receivethe motion inhibitor. The transverse bore is in communication with theinner bore and the engagement pocket. The engagement assembly furtherincludes a biasing member disposed within the transverse bore andsurrounding the motion inhibitor. The biasing member is configured tobias the motion inhibitor away from the engagement pocket. Theengagement pocket further includes a lip that acts as stop, limiting thepivotal motion of the spinal fixation rod disposed in the engagementpocket.

In another embodiment, a system for implanting a spinal fixation rodgenerally includes a spinal fixation rod and surgical instrument. Thesurgical instrument includes an engagement assembly, a transferassembly, and an actuator. The engagement assembly includes a motioninhibitor configured to releasably engage the spinal fixation rod and anengagement pocket defining a rod receiving gap configured and sized toreceive a portion of a spinal fixation rod and to permit the spinalfixation rod to pivot therein. The transfer assembly includes a shaftoperably coupled to the motion inhibitor. The actuator is operablycoupled to the shaft so as to translate the shaft upon actuation of theactuator. The movement of the shaft causes at least one of the first andsecond engagement walls to move toward the other of the first and secondengagement walls between a first position in which the rod receiving gaphas a first size and a second position in which the rod receiving gaphas a second size. The second size is less than the first size.

In one embodiment, the motion inhibitor is movable upon translation ofthe shaft to a third position in which the rod receiving gap has a thirdsize, the third size being less than the second size. The engagementassembly defines an ejection port in communication with the rodreceiving gap. The ejection port faces a direction substantiallyperpendicular to a longitudinal axis defined along a length of thesurgical instrument. The engagement pocket is contoured and sized toallow removal of the spinal fixation rod therefrom only when the spinalfixation rod is substantially perpendicular to the longitudinal axisdefined by the surgical instrument body and when the motion inhibitor isin the first position. The motion inhibitor includes an auxiliary shafthaving first and second ends. The auxiliary shaft includes a curvedbrake surface at the second end thereof. The curved brake surface isconfigured to contact the spinal fixation rod. The curved brake surfacehas a substantially concave configuration. The curved brake surface ofthe motion inhibitor is configured to receive a curve brake surface ofthe spinal fixation rod. The surgical instrument further includes asurgical instrument body defining a longitudinal axis and connected tothe actuator and the engagement assembly. The motion inhibitor includesthe second engagement wall at a distal end thereof. The surgicalinstrument body defines an inner bore extending along the longitudinalaxis. The inner bore being is and dimensioned to slidably receive theshaft. The engagement assembly defines a transverse bore configured anddimensioned to slidably receive the motion inhibitor. The transversebore is in communication with the inner bore and the engagement pocket.The engagement assembly further includes a biasing member disposedwithin the transverse bore and surrounding the motion inhibitor. Thebiasing member is configured to bias the motion inhibitor away from theengagement pocket. The engagement pocket further includes a lip thatacts as stop, limiting the pivotal motion of the spinal fixation roddisposed in the engagement pocket.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofpreferred embodiments of the application, will be better understood whenread in conjunction with the appended drawings. For the purposes ofillustrating the surgical instrument for introducing a spinal fixationrod of the present application, the drawings merely show exemplaryembodiments. It should be understood, however, that the application isnot limited to the precise arrangements and instrumentalities shown. Inthe drawings:

FIG. 1 is a perspective view of a surgical system constructed inaccordance with one embodiment including a surgical instrument and aspinal fixation rod engaged to the surgical instrument, such that thesurgical instrument is configured to insert the spinal fixation rod in apedicle screw implanted in a vertebra;

FIG. 2 is an exploded perspective view of the surgical assemblyillustrated in FIG. 1, showing the surgical instrument as including asurgical instrument housing that supports an actuator assembly, anactuating mechanism, an engagement assembly, a locking mechanism, acentering sleeve, and a tissue retractor;

FIG. 3 is a perspective view of the actuator assembly illustrated inFIG. 2, including an actuator, a grip, and a biasing member;

FIG. 4 is a perspective view of the transfer assembly and the actuatorillustrated in FIG. 2, the transfer assembly including a shaft and abiasing member;

FIG. 5A is a perspective view of the surgical instrument housingillustrated in FIG. 2;

FIG. 5B is a cross-sectional view of the housing as illustrated in FIG.5A, taken along line 5B-5B, showing an actuator, engagement member andbiasing member supported by the housing;

FIG. 6A is an exploded perspective view of the engagement assemblyillustrated in FIG. 2, the engagement assembly including an engagementbody, a lock and a biasing member;

FIG. 6B is another exploded perspective view of the engagement assemblyillustrated in FIG. 6A;

FIG. 7A is a side elevation view of the spinal fixation rod illustratedin FIG. 2;

FIG. 7B is a perspective view of the spinal fixation rod illustrated inFIG. 7A;

FIG. 8A is a perspective view of the spinal fixation rod as illustratedin FIG. 2 engaged with the engagement body as shown in FIG. 6A, and thespinal fixation rod is in a first pivotal orientation;

FIG. 8B is a perspective view of the spinal fixation rod as illustratedin FIG. 2 engaged with the engagement body as shown in FIG. 6A, and thespinal fixation rod is in a second pivotal orientation;

FIG. 9 is a perspective view of the locking mechanism as illustrated inFIG. 2;

FIG. 10A is a top elevation view of the surgical instrument illustratedin FIG. 1;

FIG. 10B is a sectional side elevation view of the surgical instrumentillustrated in FIG. 10A, taken along line 10B-10B;

FIG. 11A is a sectional side elevation view of the surgical instrumentas illustrated in 10A, taken along line 11A-11A, the surgical instrumentbeing shown in a first configuration;

FIG. 11B is a cross-sectional view of the surgical instrument asillustrated in 11A, but showing the surgical instrument in a secondconfiguration;

FIG. 11C is a cross-sectional view of the surgical instrument asillustrated in 11A, but showing the surgical instrument in a thirdconfiguration;

FIG. 12 is a perspective view of a centering sleeve and a tissueretractor;

FIG. 13A is an enlarged cross-sectional perspective view of a distalportion of the surgical instrument as illustrated in FIG. 10A, takenalong line 13A-13A, showing the primary shaft, the engagement assembly,and the spinal fixation rod while the surgical instrument is in a firstconfiguration;

FIG. 13B is an enlarged cross-sectional perspective view of the distalportion of the surgical instrument as illustrated in FIG. 13A, butshowing the surgical instrument in a second configuration; and

FIG. 13C is an enlarged cross-sectional perspective view of the distalportion of the surgical instrument as illustrated in FIG. 13A, butshowing the surgical instrument in a third configuration.

DETAILED DESCRIPTION

Referring to FIG. 1, a surgical system 8 includes a surgical instrument10, which is illustrated as a spinal fixation rod implantation tool. Itis contemplated, however, that the surgical instrument 10 can beemployed to implant other implants, such as different kinds of rods,tubes, or any other suitable elongate member, in other parts of a humanor animal body. The surgical system 8 further includes a centeringsleeve 260 that can be removably supported by the surgical instrument10, a spinal fixation rod 300 that can be releasably engaged by thesurgical instrument, a vertebral implant 400, which can be in the formof a pedicle screw that is configured to receive the spinal fixation rod300 during operation, and a tissue retractor 430. The centering sleeve260 is releasably secured to the surgical instrument 10 and the tissueretractor 430 so as to center the surgical instrument with respect tothe tissue retractor 430 and implant the spinal fixation rod 300 at apredetermined location with respect to the vertebral implant 400. Thesurgical instrument 10 is illustrated as extending along a longitudinalaxis L, a lateral axis A that extends substantially perpendicular to thelongitudinal axis L, and a transverse axis T that extends substantiallyperpendicular to the longitudinal axis L and the lateral axis A. Inaccordance with the illustrated orientation of the surgical instrument10, the lateral axis A and the longitudinal axis L extend horizontally,while the transverse axis T extends vertically. It can also be said thatthe lateral and transverse axes A and T extend radially out from thelongitudinal axis L. It should be appreciated that the longitudinal,lateral, and transverse axes are used herein with reference to theorientation of the surgical instrument 10 and its components asillustrated, and that the actual orientation of the surgical instrument10 and its components may change during use.

Referring to FIGS. 1-2, the surgical instrument 10 includes a surgicalinstrument housing 11 that supports an actuator assembly 12 at itsproximal end 39, an engagement assembly 80 at its distal end 59, whichis longitudinally opposed to the proximal end 39, and a transferassembly 150 operatively coupled to the actuator assembly 12 and theengagement assembly 80. As used herein, forward motion refers to adirection from the proximal end 39 toward the distal end 59 of thesurgical instrument housing 11, and rearward motion refers to adirection from the distal end toward the proximal end. The actuatorassembly 12 can be selectively engaged and disengaged as desired inthree configurations. In a first configuration, the actuator assembly 12allows the spinal fixation rod 300 to be inserted and removed into andfrom the engagement assembly 80. In the second configuration, theactuator assembly 12 can be engaged so as to irremovably retain thefixation rod 300 in the engagement assembly 80. While the spinalfixation rod 300 cannot be removed from the engagement assembly 80 whenthe actuator assembly 12 is in the second configuration rod, the spinalfixation rod can nonetheless pivot with respect to the surgicalinstrument housing 11. In the third configuration, the actuator assembly12 can be further engaged, causing the transfer assembly 150 to bias theengagement assembly 80 to a position in which the spinal fixation rod300 is braked with respect to pivotal movement relative to the surgicalinstrument housing 11. Thus, when the actuator assembly 12 is in thethird configuration, the engagement assembly 80 precludes, or at leastinhibits, pivotal movement of the spinal fixation rod 300 relative tothe surgical instrument housing 11.

Referring to FIG. 3, the actuator assembly 12 includes an actuator 13, agrip 40, and a biasing member 60. The actuator 13 is operably coupled tothe primary shaft (see FIG. 2) and includes an actuator body 14 thatdefines a first proximal end 15 and a longitudinally opposed seconddistal end 22. The actuator body 14 includes a plug 18 at the proximalend 15 and a longitudinally elongate shaft 26 that extends distally fromthe plug 18. The plug 18 defines an outer biasing surface 16 at itsproximal end, and an outer stop surface 17 at its distal end. The shaft26 extends from the stop surface 17 and defines a diameter orcross-sectional dimension less than that of the stop surface 17. Thebiasing surface 16 is configured to receive a longitudinally directedforce F4 and can be flat or otherwise ergonomically contoured so as tobe comfortably biased by a human finger. For instance, the biasingsurface 16 may have substantially concave shape. Alternatively, thebiasing surface 16 may be curved or textured and sized to be biased by abiasing member or other tool. The plug 18 defines an outer surface 19that extends between the biasing surface 16 and the stop surface 17. Inaccordance with the illustrated embodiment, the outer surface 19 can beround having an outer diameter D1 that tapers, decreasing as itapproaches the stop 17. The configuration of the outer surface 19 maytherefore provide the plug 18 with a substantially frusto-conical shape.Alternatively, it should be appreciated that the plug 18 could defineany suitable alternative shape as desired.

The actuator 13 can further include a channel 21 that extendstransversely into, and through, the plug 18, and is configured toreceive a portion of the biasing member 60 as described in more detailbelow. In the illustrated embodiment, the channel 21 of the plug 18 isoriented substantially parallel to the transverse axis T defined by thesurgical instrument 10 (see FIG. 1). The actuator 13 further includes anengagement member in the form of an aperture 20 that extends laterallythrough the plug 18 in alignment with the channel 21. The aperture 20 isconfigured to engage with a complementary engagement member of thebiasing member so as to connect and operably couple the biasing member60 and the plug 18. In the depicted embodiment, the aperture 20 of theplug 18 is oriented substantially parallel to the lateral axis A definedby the surgical instrument 10 (see FIG. 1). It should be appreciatedthat the channel 21 and the aperture 20 can extend partially through theplug 18 at different angles than described and can be any of a number ofshapes such as but not limited to round, square, rectangular, or otherpolygonal shapes.

The shaft 26 can include a tubular or alternatively shaped body 31 thatpresents an outer surface 27 and defines an outer diameter D2, which canbe constant or can be variable along the length of the body. The shaft26 can also include a recess 28 that extends radially into the shaftbody 31 so as to define a reduced diameter with respect to the diameterD2. The recess 28 is defined by a side surface 29 that extends radiallyin from the outer surface 27 and a tapered surface 30 that extendsradially in from the outer surface 27 and is tapered toward the sidesurface 29 (see FIG. 5B). In the illustrated embodiment, the recess 28is annular and extends radially around the entire perimeter of the body31. However, the recess 28 may have any suitable shape or configuration.For example, the recess 28 may only extend along a bottom portion of thebody 31. Regardless of its shape and configuration, the recess 28 isconfigured to releasably receive the release knob 231 as described inmore detail below.

The actuator 13 further includes an engagement member 23 carried by theshaft 26, which can be provided as a threaded bore 24 that extendslongitudinally into the second end 22 of the shaft 26. The bore 24presents internal threads 25 configured to couple the shaft 26, and thusthe actuator 13, to the transfer assembly 150 (see FIG. 4). It should beappreciated that the engagement member 23 can be provided as anystructures configured to mate with a corresponding feature on thetransfer assembly 150. For example, the engagement member 23 may be partof a snap-fit mechanism capable of connecting the shaft to the transferassembly 150.

With continuing reference to FIG. 3, the actuator assembly 12 furtherincludes a grip 40. The grip 40 includes a grip body 41, which serves asa handle for holding and manipulating the surgical instrument 10. Thegrip body 41 includes a gripping portion 42 and an attachment portion45. The gripping portion 42 has a first free end 79 and a longitudinallyopposed second end 99 connected to the attachment portion 45 and can bea pistol grip shape as shown or alternatively any other shape configuredto be easily and comfortably grasped by a human hand. The grippingportion 42 can include one or more grooves 43 disposed on the grip body41. As shown in the illustrated embodiment, a plurality of grooves 43may be disposed substantially along the entire length of the gripportion 41 between the first end 79 and the second end 99. Irrespectiveof the number of grooves 43, each groove 43 is configured and sized toreceive one or more human fingers to enhance the comfort of use and thelevel of control of the actuator assembly 12. In the depictedembodiment, the grooves 43 have a substantially concave configuration.The grip 40 can also include one or more cutouts 44 that extendlaterally through the gripping portion 42. The cutouts 44 of the grip 40can be configured as desired to provide a desired weight balance whilealso reducing the total weight of the grip 40. In addition to thecutouts 44, the grip 40 may include a guard or stop 77 at its second end99 for preventing, or at least inhibiting, a user's hand grabbing thegripping body 41 from slipping past the second end of the grip, therebyfacilitating manual control of the surgical instrument 10. Asillustrated, the guard 77 features a substantially planar configurationextending laterally from the second end 99 of the grip 40 and has anopen recess 75 configured and sized to receive a portion of the biasingmember 60.

The attachment portion 45 extends generally up from the guard 77 andincludes an attachment body 46 that defines a first lower proximal end47 and a second upper distal end 48. The attachment portion 45 isattached to the guard 77 at the proximal end 47 and to the surgicalinstrument housing 11 at the distal end 48. The second end 48 defines agap 49 that extends from the second end 48 through at least a portion ofthe attachment body 46 so as to define opposed attachment forks 50separated by the gap 49. The attachment forks 50 are substantiallyparallel to each other and are configured to attach the grip 40 to boththe surgical instrument housing 11 and the biasing member 60.

In particular, the grip 40 defines a first engagement member in the formof an outer aperture 51 that extends transversely through the attachmentforks 50 and is configured to accept a first fastener 52 to connect thegrip 40 to the surgical instrument housing 11, as illustrated in FIG. 1.The first fastener 52 may include any suitable device or mechanismcapable of coupling the grip 40 to the surgical instrument housing 11.For example, the first fastener 52 may include a pin. As illustrated inFIG. 5A, the surgical instrument 10 defines a complementary engagementmember in the form of an aperture 55 that extends transversely throughthe surgical instrument housing 11. Thus, the forks 50 are placed overthe instrument housing 11 such that the apertures 51 and 55 are inalignment, and the fastener 52 is inserted through the apertures 51 and55 so as to attach the grip 40 to the instrument housing 11. Theinstrument housing 11 can be grooved, such that the forks 50 arereceived in indented slots 192. The indented slots 192 are thereforeconfigured and dimensioned to receive the forks 50. When the forks 52are positioned in the indented slots 192 and the first fastener 52 isinserted through the apertures 51 and 55, the position of the grip 40 isfixed relative to the surgical instrument housing 11, as described inmore detail below. Referring again to FIG. 3, the grip 40 can furtherdefine a second or inner aperture 53 that extends laterally through theattachment forks 50 at a location proximal of the outer aperture 51. Theinner aperture 53 is configured to connect the grip 40 to the biasingmember 60.

In particular, the biasing member 60 includes a biasing member body 61,which provides a lever that defines a first upper proximal end 62 and anopposed second lower distal end 64. The proximal end 62 of the biasingmember body 61 is sized to fit within the channel 21 of the plug 18. Thebiasing member 60 includes an engagement member in the form of anaperture 65 that extends laterally through the biasing member body 61 atthe proximal end 62. The proximal end 62 is inserted into the transversechannel 21 of the plug 18, such that the aperture 65 is aligned with theaperture 20. A fastener 66 is inserted through the apertures 65 and 20so as to attach the biasing member 60 to the actuator 13. Asillustrated, the fastener 66 may include a pin.

The biasing member body 61 further defines a pivot portion 67 disposedbetween the proximal end distal ends 62 and 64. The pivot portion 67 issized to fit in the gap 49 of the grip 40. The biasing member body 61defines an engagement member in the form of an aperture 68 that extendslaterally through the pivot portion 67. The pivot portion 67 is insertedinto the gap 49 of the grip 40 between the attachment forks 50, suchthat the aperture 68 is aligned with the inner aperture 53 of the grip40. A fastener 54, such as a pin, is inserted through the apertures 68and 53 so as to pivotally attach the biasing member 60 to the grip 40.

During use, a surgeon can grab onto the grip 40 in order to manipulatethe actuator assembly 12, and simultaneously grasp the distal end 64 ofthe biasing member body 61. The distal end 64 can present one or moregripping grooves 63 as desired. Each gripping groove 63 is configuredand sized to receive one or more user's fingers. To this end, eachgripping groove 63 may have a concave configuration. A force F1, whichcan be a manual squeeze, can be applied to the distal end 64 of thebiasing member 60 to bias the distal end 64 toward the grip 40, causingthe biasing member body 61 to pivot about the fastener 54. This pivotalmovement of the biasing member body 61 in turn causes the proximal end62 to move longitudinally forward. Because the proximal end 62 of thebiasing member 60 is coupled to the actuator 13, the force F1 causes thebiasing member 60 to bias the actuator 13 in a forward direction, whichalso causes the transfer assembly 150 (see FIGS. 1 and 4) to translatelongitudinally forward. Alternatively, a longitudinally forward force F4can be applied directly to the biasing surface 16 of the plug 18 so asto urge the actuator 13 and transfer assembly 150 forward. In thisregard, it should be appreciated that the surgical instrument 10 can beprovided without the biasing member 60.

Referring now to FIG. 4, the transfer assembly 150 includes an actuationmember in the form of a primary shaft 152 that includes a longitudinallyelongate shaft body 170 defining a first proximal end 153 and an opposedsecond distal end 157. The primary shaft 152 defines an engagementmember provided as external threads 156 on the proximal end 153 of theshaft body 170. The threads 156 correspond to, and are configured tomate with, the internal threads 25 within the inner bore 24 of theactuator 13 so as to releasably connect the primary shaft 152 to theactuator 13. Accordingly, to secure the primary shaft 152 to theactuator 13, the shaft body 170 is aligned with the inner bore 24 andthen the primary shaft 152 and the actuator 13 are rotated with respectto one another, thereby causing the threads 156 and 25 to mate. Theeffective length of the coupled primary shaft 152 and actuator 13 can beadjusted by how far the post primary shaft 152 is screwed into the innerbore 24. The threaded connection allows the effective length to beadjusted as desired to correct for variances in tolerances of themanufactured parts of the surgical instrument 10. As discussed above,the threads 156 and 25 may be replaced by any other device, apparatus ormechanism suitable for releasably connecting the shaft 152 to theactuator 13.

The elongate body 170 has a rod-like shape that defines a longitudinallength L1 and presents an outer surface 171 that extends radiallyoutward from the longitudinal axis L. The outer surface 171 can be roundor otherwise shaped as desired, extends along a portion of thelongitudinal length L1 of the elongate body 170, and defines an outerdiameter or cross-sectional dimension D21. The elongate body 170 definesa raised portion 172 that presents an outer diameter D3 orcross-sectional dimension that is larger than the outer diameter orcross-sectional dimension D21 defined by the outer surface 171.Alternatively, the outer diameter D21 defined by the outer surface 171may be equal or substantially similar to the outer diameter orcross-sectional dimension D3 of the raised portion 172. In otherembodiments, the outer diameter or cross-sectional dimension of theelongate body 170 remains constant along the length L1.

The primary shaft 152 includes an engagement member provided as aconnection link 158 at the second end 157 of the shaft body 170. Theconnection link 158 has a round shape or any other suitable shape andhas an outer diameter or cross-sectional dimension D4. In the depictedembodiment, the outer diameter or cross-sectional dimension D4 of theconnection link 158 is greater than the outer diameter orcross-sectional dimension D21 defined by outer surface 171 andsubstantially similar to the outer diameter or cross-sectional dimensionD3 of the raised portion 172. In alternative embodiments, the outerdiameter or cross-sectional dimension D4 of the connection link 158 issubstantially similar to the outer diameter or cross-sectional dimensionD21 defined by the outer surface 171. The primary shaft 152 defines agap 163 extending longitudinally into the second end 157 of the shaftbody 170 so as to define opposed tips 160. The gap 163 terminates at abeveled shaft surface 162 that is sloped transversely downward along alongitudinally forward direction. The opposing tips 160 each include acurved engagement surface 164 that is configured to operatively couplethe primary shaft 152 to the engagement assembly 80 (see FIG. 2), asdescribed in more detail below.

With continuing reference to FIG. 4, the transfer assembly 150 furtherincludes a biasing member, which can be a coil spring 201 that definesan inner diameter or cross-sectional dimension D5 and an outer diameteror cross-sectional dimension D6. The inner diameter D5 is greater thanthe outer diameter D3 of the raised portion 172 of the elongate shaftbody 170 and less than the outer diameter D2 of the actuator 13. Thisallows the primary shaft 152 to be disposed within the spring 201 andprevents, or at least inhibits, the actuator 13 from being disposedwithin the spring 201. The spring 201 can be captured between the distalend 22 of the actuator 13 and a seat 197 of the surgical instrumenthousing 11 (see FIG. 5B). Accordingly, the spring 201 provides a springforce that biases the actuator 13 longitudinally rearward toward itsdisengaged position, such that forward motion of the actuator 13, andthus the primary shaft 152, relative to surgical instrument housing 11is against the spring force.

Referring to FIGS. 5A and 5B, the surgical instrument housing 11includes a longitudinally elongate tubular body 181 that defines a firstproximal end 182 and a longitudinally opposed second distal end 183. Theproximal end 182 is attached to the grip 40 as described above withreference to FIGS. 2 and 3. The surgical instrument housing 11 furtherincludes an engagement body 81 that is attached, for instancemonolithically attached, to the second end 183 of the tubular body 181.The tubular body 181 defines an inner bore 184 which extendslongitudinally between and through the proximal and distal ends 182 and183. The proximal end 182 of the tubular body 181 defines an innerdiameter or cross-sectional dimension D7 of the inner bore 184.

The housing body 181 presents an outer surface 185 that defines an outerdiameter or cross-sectional dimension D8. The inner diameter D7 of theinner bore 184 is at least slightly greater than the outer diameter D6of the spring 201, such that the spring 201 can be disposed in the innerbore 184 at the proximal end 182 of the housing body 181. The housingbody 181 includes an inner shoulder 199 defining a seat surface 197located distally of the portion of the inner bore 184 defining innerdiameter D7. The seat surface 197 defines an inner diameter less thanthe inner diameter D7, and further less than the inner diameter D5 ofthe coil spring 201. Accordingly, one end of the coil spring 201 sitsagainst the seat surface 197, and an opposed end of the coil spring 201sits against the distal end 22 of the actuator 13 as described above.The inner diameter of the seat surface 197 is also slightly greater thanthe outer diameter D3 of the elongate shaft body 170, such that theshaft 152 is slidably received in the housing body 181.

The surgical instrument housing 11 includes a grip mount 186 thatextends transversely down from the first end 182 of the housing body181. Opposed lateral sides of the grip mount 186 define an indented slot192 configured to receive the attachment forks 50 of the grip 40. Thesurgical instrument housing 11 further defines an aperture 55 thatextends laterally through the grip mount 186 at a location aligned withthe indented slots 192. To attach the grip 40 to the housing body 181the attachment forks 50 are slid into the indent slots 192 until theouter aperture 51 of the grip 40 is aligned with the aperture 55 of thesurgical instrument housing 11 (see also FIG. 3). The fastener 52 isthen inserted through the apertures 55 and 51. Once the fastener 52 hasbeen inserted, the grip 40 and the housing body 181 are attached andunable to rotate with respect to one another. The surgical instrumenthousing 11 further defines a transverse aperture 191 that extends intothe bottom end of the grip mount 186 and into the inner bore 184 of thehousing body 181. The grip mount 186 is configured to support a lockingmechanism 220, such that a locking shaft 221 of the locking mechanismextends through the second aperture 191, as described in detail below(see FIG. 9).

The surgical instrument housing 11 can also include a longitudinallyelongate projection 195 that extends transversely down from the housingbody 181. The projection 195 provides additional strength and rigidityto the housing body 181. Additionally, the surgical instrument housing11 can define a number of openings 196 located as desired which extendfrom the outer surface 185 into the inner bore 184. The openings 196 canhave an elongate slot shape as shown and can facilitate cleaning andsterilization of the surgical instrument 10. Thus, one of skill in theart will realize that the size, shape and orientation of the openings196 can vary as desired. In another alternative embodiment, the surgicalinstrument housing 11 can have no openings 196. As discussed in detailbelow with respect to FIG. 12, the surgical system 8 may include acentering sleeve 260 (see FIGS. 1 and 12) that can be releasably securedto the surgical instrument 10 and the tissue retractor 430 so as tocenter the surgical instrument with respect to the tissue retractor 430and implant the spinal fixation rod 300 at a predetermined location withrespect to the vertebral implant 400. The surgical system 8 can be usedwithout the centering sleeve 260 and, in such a case, the projection 195of the surgical instrument housing 11 can act as a centering spacer whenthe surgical instrument housing is placed within the tissue retractor430 so as to center the surgical instrument 10 relative to the tissueretractor 430 and implant the spinal fixation rod 300 at a predeterminedposition with respect to the tissue retractor 430.

Referring to FIGS. 6A and 6B, the engagement assembly 80 includes theengagement body 81 of the surgical instrument housing 11, a spinalfixation rod motion inhibitor or brake 120, and a biasing member whichcan be provided as a coil spring 141. The motion inhibitor 120 isoperably coupled to the primary shaft 152 (see FIG. 2). The engagementbody 81 defines a first proximal portion 82 attached to the second end183 of the housing body 181 and a second distal portion 83 that extendslongitudinally forward and transversely down from the first proximalportion 82. The transverse offset of the second distal portion 83relative to the first proximal portion 82 facilitates proper positioningof the spinal fixation rod 300 (see FIG. 8A) when implanted in aplurality of pedicle screws within the patient's body. The engagementbody 81 presents an outer surface 84 and also defines a transverse bore85 that extends transversely down into the outer surface 84 of theproximal portion 82, intersects the inner bore 184 of the housing body181, and terminates in the second distal portion 83.

The second distal portion 83 includes an engagement tip 86, whichdefines an outer lip 87, a first engagement wall 73 that carries acorresponding first engagement surface 88, which can be a curved orconcave lower surface, extending into the interior of the second distalportion 83 from the lip 87 and laterally opposed retaining walls 89. Thelip 87, lower surface 88 and opposing retaining walls 89 form anengagement pocket 90. The curvature of the lower surface 88substantially matches the curvature of an end portion of the spinalfixation rod 300 so that such end portion of the spinal fixation rod canbe securely retained within the pocket 90. The pocket 90 extends intothe engagement body 81 and intersects with the inner bore 85. Theretaining walls 89 define laterally opposed vertical interior surfaces93. The interior surfaces 93 are connected by a curved or concavelateral beam 92 disposed in the second distal portion 83. The curvedlateral beam 92 can be contoured so as to match the outer curved surfaceof the spinal fixation rod 300.

The retaining walls 89 each further includes a bottom surface 95 that iscurved in a substantially vertical plane. The lower surface 88 and thebottom surface 95 are separated and define a retention gap 91therebetween. The retention gap 91 is shaped to receive a correspondingsurface of the spinal fixation rod 300 such that once the spinalfixation rod 300 is engaged within the pocket 90, the spinal fixationrod 300 can only be removed from the pocket 90 when the spinal fixationrod 300 is oriented substantially perpendicular to the longitudinal andlateral axes L and A and substantially parallel to the transverse axis Tdefined by the surgical instrument 10 (see FIG. 1). In alternateembodiments, once the spinal fixation rod 300 has been positioned withinthe pocket 90, it can only be removed from the pocket when oriented inother positions or orientations. For instance, in some embodiments, thespinal fixation rod 300 can only be removed from the pocket 90 when thespinal fixation rod is oriented substantially parallel to thelongitudinal axis L defined by the surgical instrument 10 (see FIG. 1).In yet other embodiment, the spinal fixation rod 300 can only bewithdrawn from the pocket 90 when it is oriented at an angle relative tothe transverse axis T defined by the surgical instrument 10 (see FIG.1). Although the spinal fixation rod 300 cannot be removed from thepocket 90 when oriented at a particular orientation, as discussed above,the curvature of the lower surface 88 and the configuration of thebottom surface 95 of the engagement assembly 80 allow the spinalfixation rod 300 to pivot relative to the engagement tip 86 between afirst position and a second position. In the first position, the spinalfixation rod 300 is oriented substantially parallel to the transverseaxis T, whereas, in the second position, the spinal fixation rod isoriented at an obtuse angle relative to the longitudinal axis L. Thefirst and second positions of the spinal fixation rod 300 maynevertheless vary in other embodiments. For example, in alternateembodiments, the spinal fixation rod 300 may be oriented substantiallyparallel to the longitudinal axis L when located in the second position.

The motion inhibitor or brake 120 defines an auxiliary shaft 121 that isa rod-like member having an outer diameter or cross-sectional dimensionD9. The auxiliary shaft 121 is disposed within the inner bore 85; thus,the outer diameter D9 is smaller than the diameter or cross-sectionaldimension of the inner bore 85. The auxiliary shaft 121 also includes anauxiliary shaft body 122 that defines a first proximal end 123 and anopposed second distal end 124. The proximal end 123 defines a topsurface 125, which is shaped such that, when the auxiliary shaft 121 isat rest with no external forces acting upon it and disposed within theinner bore 85, the top surface 125 is substantially parallel to, andrecessed within, the outer surface 84 of the first portion 82 of theengagement body 81. The motion inhibitor 120 defines cutouts extendinginto the auxiliary shaft body 122 so as to define an indented portion128 that has a reduced cross-sectional dimension D20 relative to therest of the auxiliary shaft 121. The indented portion 128 defines a pairof engagement surfaces 129 configured to engage the curved engagementsurface 164 on the tips 160 of the primary shaft 152 (see FIG. 4). Thedistal end 124 of the auxiliary shaft body 122 has a reduced outerdiameter or cross-sectional dimension D9 compared to the first end 123.This abrupt change in outer diameter D9 occurs at a transition 127,which provides a spring seat 130. The distal end 124 terminates at asecond engagement wall 119 that defines a corresponding secondengagement surface 131, which can be defined as a curved or concavebrake surface as illustrated, which may be substantially concave.

The engagement assembly 80 defines a variable-sized rod receiving gap 94that can be shaped and sized to receive a portion of the spinal fixationrod 300 and to permit the spinal fixation rod to pivot inside the pocket90 when the rod receiving gap 94 defines a first size, and further toretain a portion of the spinal fixation rod 300 when the rod receivinggap 94 defines a second size that is less than the first size (see FIGS.8A-B). The rod receiving gap 94 is further configured to define a thirdsize that is less than the second size, such that the engagementassembly 80 can prevent movement of the spinal fixation rod 300 insidethe rod receiving gap 94. The rod receiving gap 94 can be defined by andbetween the first engagement wall 73, and thus the corresponding firstengagement surface 88, and the second engagement wall 119, and thus thecorresponding second engagement surface 131. As is described in moredetail below, at least one of the first and second engagement walls 73and 119 is movable toward the other from a first position to a secondposition so as to change the size of the rod receiving gap 94 from thefirst size to the second size, respectively, and further from the secondposition to a third position so as to change the size of the rodreceiving gap 94 from the second size to the third size. For instance,the primary shaft 152 is operably coupled to the movable engagement wall119, such that translation of the primary shaft 152 causes the movableengagement wall 119 to move with respect to the other engagement wall73. The engagement assembly 80 further defines an ejection port 135shaped and sized to receive a portion of the spinal fixation rod 300.The ejection port 135 is in communication with the rod receiving gap 94and can be defined by and between the retaining walls 89 and the lip 87.In the depicted embodiment, the ejection port 135 faces a directionsubstantially perpendicular to a longitudinal axis L (see FIG. 1)defined along the length of the surgical instrument 10 to removal of thespinal fixation rod 300 from the engagement pocket 90 only when thespinal fixation rod is substantially perpendicular to the longitudinalaxis L defined by the surgical instrument 10 and when at least one ofthe first and second engagement walls 73 and 119 is in the firstposition. At least one of the retaining walls 89 and a lip 87 extendsubstantially perpendicular to the longitudinal axis L defined along thelength of the surgical instrument at the ejection port 135.

The curvature of the curved brake surface 131 is substantially equal tothe curvature of a curved top brake surface 311 of a brake 307 of thespinal fixation rod 300 (see FIGS. 7A-B). The top brake surface 311 ofthe brake 307 may have a substantially convex shape. As discussed indetail below, the motion inhibitor 120 can move along a first ordisengaged position, a second or engaged position, and a third orbraking position. When the motion inhibitor 120 is in the firstposition, the rod receiving gap 94 (see FIGS. 6A-B) has a first size andthe curved brake surface 131 is positioned outside the engagement pocket90. Consequently, the curved brake surface 131 does not engage orcontact the curved top surface 311 of the spinal fixation rod 300. Inthe second position, the motion inhibitor 120 is at least partiallypositioned inside the engagement pocket 90 and the rod receiving gap 94(see FIGS. 6A-B) has a second size, which is less than its first sizewhen the motion inhibitor 120 is in the first position. Additionally,when the motion inhibitor 120 is in the second position, its brakesurface 131 abuts or contacts the curved top surface 311 of the spinalfixation rod 300, thereby preventing removal of the spinal fixation rod300 from the pocket 90. When the motion inhibitor 120 is in the thirdposition, the rod receiving gap 94 (see FIGS. 6A-B) has a third size,which is less than its second size when the motion inhibitor 120 is inthe second position. Moreover, when the motion inhibitor 120 is in thethird position, its brake surface 131 functions as a brake and thecurved brake surface 131 exerts pressure against the curved top surface311 of the spinal fixation rod 300 to prevent, or at least inhibit, thespinal fixation rod 300 from pivoting with respect to the surgicalinstrument 10.

The spring 141 defines an inner diameter or cross-sectional dimensionD10 and an outer diameter or cross-sectional dimension D11. The innerdiameter D10 of the spring 141 is greater than the reduced outerdiameter D9 of the second end 124 of the auxiliary shaft 121 and lessthan the cross-sectional dimension D20 of the first end 123 of theauxiliary shaft 121. The inner diameter D10 of the spring 141 is alsogreater than a portion of the inner bore 85 located in the second distalportion 83 of the engagement body 81 and adjacent a seat 169 (see FIG.11A). The outer diameter D11 of the spring 141 is greater than its innerdiameter D10 but smaller than the diameter of the inner bore 85. Thespring 141 can therefore be disposed within the inner bore 85, such thatthe distal end 124 of the auxiliary shaft 121 is disposed within thespring 141 and the proximal end of the spring 141 seats against thespring seat 130. The engagement body 81 further defines a seat 169 inits second distal portion 83 for the spring 141 disposed within theinner bore 85, such that the spring 141 extends between the seat 169 inthe bore 85 and the spring seat 130 (see FIG. 11A). The spring 141provides a spring force that biases the motion inhibitor or brake 120proximally, away from the pocket 90 of the engagement assembly 80.Hence, if a spinal fixation rod 300 is partially disposed within thepocket 90, the spring 141 biases the motion inhibitor or brake 120 awayfrom the spinal fixation rod 300. In other words, the spring 141 biasesthe motion inhibitor or brake 120 toward its first or disengagedposition.

Referring now to FIGS. 7A-B the spinal fixation rod 300 includes a rodbody 301, which presents an outer surface 302 having an outer diameteror cross-sectional dimension D12. The rod body 301 is elongate from afirst proximal end 304 to a second distal end 303 along a central rodaxis 317. The rod body 301 includes a nose 305 at the distal end 303,which as shown is bullet-shaped to facilitate entry into a patient'sbody. The spinal fixation rod 300 includes a linkage 316 that extendsfrom the proximal end 304 of the rod body 301. The linkage 316 includesa brake 307 and at least one engagement rail 306. In the illustratedembodiment, the linkage 316 includes a pair of engagement rails 306supported on opposite lateral sides of the brake 307. The engagementrails 306 facilitate insertion of the spinal fixation rod 300 into thepocket 90 and also inhibit inadvertent removal of the spinal fixationrod 300 from the pocket 90. The brake 307 is configured to selectivelyengage the motion inhibitor 120 to prevent the spinal fixation rod 300from pivoting in the pocket 90.

The engagement rails 306 are defined by a first sloped engagementsurface 308, a second sloped engagement surface 309 angularly offsetwith respect to the first sloped engagement surface 308, and a curvedengagement surface 310 opposite the first and second sloped engagementsurfaces 308 and 309. The first and second sloped engagement surfaces308 and 309 meet at an intersection 315, and define a V-shape, whichcorresponds to the top surface 95 of the engagement tip 86 of theengagement assembly 80 (see FIG. 6B). The curved engagement surface 310is shaped to correspond to the lower surface 88 of the engagement tip86. Thus, the spinal fixation rod 300 is inserted into the pocket 90 byplacing the rod 300 in a transverse orientation and inserting theengagement rails 306 into the mouth of the gap 91 between the retainingwalls 89 and the lower surface 88 (FIG. 8A), and subsequently pivotingthe spinal fixation rod 300 so that the engagement rails 306 arereceived in the gap 91 (FIG. 8B).

With continuing reference to FIGS. 6A-7B, the brake 307 includes acurved top brake surface 311 and opposing side walls 312 extending fromthe curved top brake surface 311, such that the engagement rails 306project laterally out from the side walls 312. The opposing side walls312 are separated by a distance which defines a length L2. The length L2is sized to allow the brake 307 to fit within the gap 91 in theengagement tip 86 between the opposed retaining walls 89. The curvatureof the curved top brake surface 311 of the brake 307 is substantiallysimilar to the curvature of the curved brake surface 131 of the motioninhibitor 120. As will be appreciated from the description below, thebrake surface 131 of the motion inhibitor 120 is configured toselectively act against the curved top brake surface 311, therebypreventing, or at least inhibiting, the spinal fixation rod 300 frompivoting with respect to the surgical instrument 10. Thus, the curvedtop brake surface 311 of the spinal fixation rod 300 can also bereferred to as a brake surface.

The spinal fixation rod 300 further includes a first notch 313 and anopposed second notch 314 each extending from the outer surface 302toward the central axis 317 at the interface between the rod body 301and the linkage 316. The second notch 314 is sized to receive to the lip87 of the engagement tip 86 when the maximum pivotal orientation of thespinal fixation rod 300 has been reached. In this regard, the lip 87 canbe referred to as a stop that limits the pivotal movement of the spinalfixation rod 300 relative to the surgical instrument 10.

Referring now also to FIG. 8A, just as the spinal fixation rod 300 canbe inserted into the pocket 90 in a first angular transverseorientation, the spinal fixation rod 300 can also be removed from thepocket 90 in the transverse orientation. When the spinal fixation rod300 is in the first orientation as shown, a substantially transverselyoutwardly directed force F2 applied to the spinal fixation rod 300, oran opposite force applied to the engagement tip 86 results in therelease of the spinal fixation rod 300 from the pocket 90. A forceapplied in any other direction will not allow the spinal fixation rod300 to be released from the pocket 90. Laterally outward movement of thespinal fixation rod 300 within the pocket 90 is prevented byinterference between the corresponding interior lateral surfaces 93 ofthe engagement tip 86 and the side walls 312 of the spinal fixation rod300. Longitudinally outward movement of the spinal fixation rod 300within the pocket 90 is prevented by interference between thecorresponding outer surface 302 of the spinal fixation rod 300 and thecurved lateral beam 92 of the engagement tip 86 in one direction and thecorresponding curved engagement surface 310 and the lower surface 88 inthe other direction. Thus, in the illustrated embodiment, the spinalfixation rod 300 is removable from the pocket 90 in only one transversedirection (i.e., when the spinal fixation rod 300 is orientedsubstantially parallel to the transverse axis T relative to the surgicalinstrument 10). As will be appreciated from the description below, thespinal fixation rod 300 can be removed only when the actuator assembly12 is disengaged.

Referring now also to FIG. 8B, the spinal fixation rod 300 is shownengaged with the pocket 90 of the engagement tip 86 in a secondorientation that is angularly offset with respect to the firstorientation. In this second orientation, the spinal fixation rod 300 isoriented at an acute angle relative to the transverse axis T. When thespinal fixation rod 300 is in the second orientation, the spinalfixation rod 300 cannot be removed from the pocket 90. Lateral movementof the spinal fixation rod 300 within the pocket 90 is prevented byinterference between the corresponding interior lateral surfaces 93 ofthe engagement tip 86 and the side walls 312 of the spinal fixation rod300. Longitudinal movement of the spinal fixation rod 300 within thepocket 90 is prevented by interference between the corresponding secondsloped engagement surface 309 of the spinal fixation rod 300 and thebottom surface 95 of the engagement tip 86 in one direction and thecorresponding curved engagement surface 310 and the lower surface 88 inthe other direction. Transverse movement of the spinal fixation rod 300within the pocket 90 is prevented by interference between thecorresponding curved top surface 311 (See FIG. 7B) and the brake surface131 (or alternatively the second sloped engagement surface 309 and thebottom surface 95) in one direction and the corresponding curvedengagement surface 310 and the lower surface 88 in the other direction.Thus, when the spinal fixation rod 300 is disposed within the pocket 90in the second orientation (or any orientation other than parallel to thefirst direction) the spinal fixation rod 300 is not removable from thepocket 90.

Referring now to FIG. 9-10B, the surgical instrument housing 11 supportsa locking mechanism 220 including a locking shaft 221, a releaseactuator illustrated as a release knob 231 attached to the locking shaft221, a bracket 232, and a biasing member illustrated as a spring 242that receives the locking shaft 221. The locking shaft 221 has an outersurface 224 defining an outer diameter or cross-sectional dimension D13.The outer diameter D13 of the locking shaft 221 is sized so that thelocking shaft 221 can be disposed within the transverse aperture 191that extends into the bottom end of the grip mount 186 (see FIG. 10B).The locking shaft 221 includes a head 225 and an elongate post 226extending from the head 225 substantially parallel to the transverseaxis T. The head 225 has a collar 227 that defines a top surface 228 anda transversely opposed bottom surface 229. A key 230 extends up from thetop surface 228 of the collar 227 and terminates at a channel 238. Thekey 230 further contains a flat transverse wall 237 and an engagementmember illustrated as a curved engagement wall 240 that defines thechannel 238. The engagement wall 240 is sized to fit in the recess 28 ofthe actuator 13. The post 226 extends down from the bottom surface 229of the collar 227. The locking shaft 221 defines a first aperture 239that extends laterally through the post 226. The spring 242 receives thepost 226 and the outer surface 224 of the locking shaft 221, and seatsagainst the bottom surface 229 of the collar 227.

With continuing reference to FIGS. 9-10B, the bracket 232 defines a topsurface 234, a bottom surface 235, and outer perimeter 236 extendingbetween the top and bottom surfaces. The bracket 232 is mounted (e.g.,welded or otherwise attached) to the grip mount 186, such that the topsurface 234 abuts the transverse bottom surface 189 of the grip mount186. The bracket 232 defines an inner bore 244 configured to receive thepost 226. The inner bore 244 extends through the bracket 244 past thetop surface 234 and bottom surface 235 and through a spring support 249.The spring support 249 of the bracket 232 protrudes from the top surface234 in a direction substantially parallel to the transverse axis T. Inthe depicted embodiment, the spring support 249 has a substantiallycylindrical shape and can provide lateral support to spring 242 whenmounted within the grip mount 186. The spring support 249 includes aninner shoulder 251 at an end adjacent to the top surface 234. The innershoulder 251 changes the diameter of the inner bore 244. Accordingly,the diameter of the inner bore 244 is greater within the spring support249 than between the top surface 234 and the bottom surface 235. Theportion of the inner bore 244 within the spring support 249 canaccommodate the spring 242 and the locking shaft 221, whereas theportion of the inner bore 244 between the top surface 234 and the bottomsurface 235 can only accommodate the locking shaft 221. Aside fromchanging the diameter of the inner bore 244, the shoulder 251 defines aspring seat 247 suitable for supporting the spring 242. The release knob231 is knob-shaped and defines an inner transverse bore 233 extendingtherethrough. Alternatively, the release knob 231 can be any shapesuitable for any desired purpose. For instance, the release knob 231 canbe configured and shaped so that it can be easily gripped by a humanhand. The release knob 231 as illustrated can also include grooves 241for improving the ability to grip the release knob 231. Alternatively,the release knob 231 can be devoid of grooves 241 or other features thatenhance the ability to grip the release knob 231. When the inner bores233 and 244 are aligned, the post 226 can be passed through them. Therelease knob 231 defines a second aperture 243 extending laterallytherethrough that is aligned with the first aperture 239 when the post226 is disposed in the bore 233. The locking mechanism 220 furtherincludes a fastener 245, such as a pin, that is inserted through thealigned first and second apertures 239 and 243 to couple the releaseknob 231 to the locking shaft 221. The bracket 232 is disposed betweenthe release knob 231 and the locking shaft 221, and defines a springseat 247, such that the spring 242 extends between the spring seat 247of the bracket 232 and the lower surface 229 of the collar 227 while thespring support 249 provides lateral support to the spring 242 Thus, thespring 242 provides a spring force that biases the locking shaft 221upward toward the actuator 13.

During operation, the spring 242 biases the locking shaft 221transversely up such that the engagement wall 240 is disposed in therecess 28 of the actuator 13. Interference between the locking shaft 221and the actuator 13 prevents the spring 201 from biasing the actuator13, and thus primary shaft 152, longitudinally rearward (see also FIG.4). A downwardly directed force F3 can be applied to the release knob231, which causes the locking shaft 221 to translate transversely downagainst the biasing force of the spring 242 until the key 230 is removedfrom the recess 28 and is thus out of interference with inner bore 184of the housing body 181. Once the locking shaft 221 is out ofinterference with the actuator 13, the spring 201 biases the actuator 13and the primary shaft 152 longitudinally rearward. The spring 201 iscompletely decompressed while the actuator 13 is disposed in thesurgical instrument housing 11, and interference between the biasingmember 60 and the actuator 13 prevents the actuator 13 and the primaryshaft 152 from being completely removed from the surgical instrumenthousing 11. Once the force F3 is removed, the spring 242 biases thelocking shaft 221 toward the primary shaft 152 until the engagement wall240 abuts the elongate shaft 26 of the actuator 13.

Referring to FIGS. 11A-C and 13A-13C, the surgical instrument 10 isshown in three configurations that occur during the normal operation ofthe surgical instrument 10. Referring first to FIGS. 11A and 13A, thesurgical instrument 10 is shown in a first configuration representing asteady state with no external forces being applied to the surgicalinstrument 10. In the first configuration, the actuator 13 is disengagedwith the plug 18 such that the recess 28 is disposed proximal of the key230, and the engagement wall 240 is not disposed in the recess 28. Alsoin the first configuration, the curved engagement surface 164 on thetips 160 of the primary shaft 152 are disposed proximal of the motioninhibitor 120; thus, the primary shaft 152 does not urge the engagementsurface 129 of the motion inhibitor 120 toward the engagement tip 86. Inother words, the primary shaft 152 does not engage or contact the motioninhibitor 120 when the surgical instrument 10 is in the firstconfiguration. The spinal fixation rod 300 is disposed within the pocket90 in the first transverse orientation. In the first configuration, thebrake surface 131 of the motion inhibitor 120 is spaced apart from thecurved top brake surface 311 of the brake 307, such that the spinalfixation rod 300 is free to rotate within the pocket 90 between thefirst orientation (FIG. 8A) and the second orientation (FIG. 8B) and thespinal fixation rod 300 can be removed from the pocket 90 with theapplication of the force F2 applied to the spinal fixation rod 300 inthe direction of the arrow when the spinal fixation rod is in the firstorientation. As stated above, if the spinal fixation rod 300 is in anyorientation other than the first orientation illustrated in FIGS. 11Aand 13A, applying force to the spinal fixation rod 300 will not resultin its release from the pocket 90. In the first configuration, thespinal fixation rod 300 can be inserted into the pocket 90.

Referring to FIGS. 11B and 13B, the surgical instrument 10 can be movedfrom the first configuration to the second configuration by actuatingthe actuator 13. To do so, a force F4 is applied to the actuator 13either via the biasing member 60 or directly to the biasing surface 16.To apply a longitudinally forward force F4 indirectly through thebiasing member 60, the user may apply a force F1 to the biasing member60 to move the biasing member 60 toward the grip 40. As the biasingmember 60 moves toward the grip 40, the first upper proximal end 62(FIG. 3) of the biasing member 60 applies a longitudinally forward forceF4 to the actuator 13. The application of the force F4 urges theactuator 13 and the connected primary shaft 152 in a longitudinallydistal direction (as indicated by arrow A in FIG. 13B) further into theinner bore 184 of the housing body 181 until the recess 28 is alignedwith the key 230. When the recess 28 and key 230 are aligned, the spring242 urges the key 230 into the inner bore 184 until the engagement wall240 is inserted into the recess 28. In this second configuration, thelongitudinally proximal translation of the actuator 13 and the primaryshaft 152 away from the engagement assembly 80 is prevented by theinterference between the flat transverse wall 237 of the key 230 and theside wall 29.

As the primary shaft 152 translates longitudinally forward to the secondconfiguration in the direction indicated by arrow A, the curvedengagement surfaces 164 on the tips 160 of the primary shaft 152 (FIG.4) contact the engagement surface 129 of the motion inhibitor 120 (FIG.6B) and urge the motion inhibitor 120 toward the engagement tip 86within the inner bore 85 (in the direction as indicated by arrow B).Once the surgical instrument 10 is in the second configuration, thebrake surface 131 of the motion inhibitor 120 has entered the pocket 90and is either slightly spaced from the curved top surface 311 of thebrake 307, or abuts the curved top surface 311 but not under pressurethat is substantial enough to cause the brake surface 131 to prevent, orat least inhibit, the spinal fixation rod 300 from pivoting in thepocket 90. Therefore, when the surgical instrument 10 is in the secondconfiguration, the spinal fixation rod 300 is able to pivot in thepocket 90.

Furthermore, when the surgical instrument 10 is in the secondconfiguration, the spinal fixation rod 300 is unable to be removed fromthe pocket 90 regardless of its angular orientation. In particular, theprevious direction of removal of the spinal fixation rod 300 is nowblocked by the interference between the brake surface 131 and the curvedtop surface 311 of the brake 307. In this regard, the brake surface 131and the lip 87 define a circumferential distance therebetween of greaterthan 180° such that the brake 307 (FIGS. 7A-7B) is captured between thebrake surface 131 and the lip 87. Thus, the brake surface 131 and thelip 87 provide a lock that precludes removal of the spinal fixation rod300 from the surgical instrument 10 in the second configuration.

As described with reference to FIG. 4, it should be appreciated that theposition of the brake surface 131 of the auxiliary shaft 121 relative tothe brake surface 311 of the spinal fixation rod 300 in the secondconfiguration can be tuned by rotating the shaft 152 and/or the actuator13 relative to each other, which causes the shaft 152 to advance forwardor retract rearward as the threads 156 and 25 engage. As the shaft 152advances forward, the curved engagement surface 164 is brought intofurther contact with the engagement surface 129 of the of the auxiliaryshaft 121 and urges the auxiliary shaft 121, and thus, the brake surface131, further toward the curved top surface 311. Conversely, as the shaft152 is retracted rearward, the curved engagement surface 164 translatesaway from the engagement surface 129 of the of the auxiliary shaft 121,such that the force of the spring 141 (see FIGS. 6A-B) urges theauxiliary shaft 121, and thus the brake surface 131, away from the brakesurface 311. Thus, the threaded connection between the actuator 13 andthe shaft 152 can be adjusted such that the brake surface 131 does notprevent the spinal fixation rod 300 from pivoting in the pocket 90, butprovides a lock in combination with the lip 87 that prevents the spinalfixation rod 300 from being removed from the pocket 90.

Referring now to FIGS. 11C and 13C, the surgical instrument 10 is shownin the third configuration. To reach the third configuration from thesecond configuration, a user once again actuates the actuator 13. To doso, a further longitudinally forward force F5 is applied to the actuator13 either via the biasing member 60 or directly to the actuator 13, sothat the actuator 13 and the primary shaft 152 translate furtherlongitudinally forward. As discussed above, the user may applylongitudinally forward force F5 to the actuator 13 by applying a forceF6 to the biasing member 60 to urge its first upper proximal end 62(FIG. 3) forward. In turn, the first upper proximal end 62 of thebiasing member 60 applies the longitudinally forward force F5 to theactuator 13. Further forward translation of the primary shaft 152 in thedirection indicated by arrow C causes the engagement surface 164 to urgethe complementary engagement surface 129 of the motion inhibitor 120distally in the direction indicated by arrow D toward the curved topsurface 311, which in turn causes the brake surface 131 to exertsufficient pressure against the curved top surface 311 to prevent, or atleast inhibit, the spinal fixation rod 300 from pivoting in the pocket90. In particular, the pressure between the brake surface 131 and thecurved top surface 311 creates a frictional force that resists anexternally applied pivotal force to the spinal fixation rod 300, therebyprecluding, or at least hindering, pivotal movement of the spinalfixation rod 300 relative to the surgical instrument 10. In the thirdconfiguration, the brake surface 131, in combination with the lip 87,continues to provide a lock that prevents the spinal fixation rod 300from being removed from the pocket 90 regardless of the angularorientation of the spinal fixation rod.

The surgical instrument 10 can be returned from the third configurationto the second configuration by removing the force F6 from the biasingmember 60 and/or the force F5 from the actuator 13, which causes thebrake surface 131 to be removed from braking engagement with the brakesurface 311. The surgical instrument 10 can be returned to the firstconfiguration by applying the downward force F3 onto the release knob231, which causes the actuator assembly 12 to assume a disengagedconfiguration. In particular, the engagement wall 240 is removed fromthe recess 28 of the actuator 13, such that the spring 201 (FIG. 5B)biases the actuator 13 rearward, thereby causing the primary shaft 152to translate rearward away from the auxiliary shaft 121. Removal ofinterference between the primary shaft 152 and the auxiliary shaft 121allows the biasing force provided by the spring 141 (FIG. 6A) totranslate the auxiliary shaft, and thus the brake surface 131, away frombrake surface 311 of the spinal fixation rod 300.

Referring now to FIG. 12, the surgical system 8 further includes acentering sleeve 260 that can be removably attached to the surgicalinstrument 10. The centering sleeve 260 includes a substantially tubularcentering sleeve body 261 that defines a first proximal end 262, anopposed second distal end 263 and an elongate portion 264 extending fromthe proximal end 262 to the distal end 263. The elongate portion 264presents an inner surface 265 that defines an inner diameter D14 and anouter surface 266 that defines an outer diameter D15. The inner surface265 of the elongate portion 264 also defines a channel 267, whichextends through the first end 262 and the second end 263. The channel267 has an open end 275 configured to receive the outer surface 185 ofthe housing body 181 (see FIG. 5A), such that the centering sleeve body261 fits over the housing body 181. The channel 267 is oblong and sizedto snugly receive the outer surface 185 of the housing body 181, whichcan also be oblong. Therefore, the centering sleeve 260 fits onto thehousing body 181 in a predetermined orientation.

With continuing reference to FIG. 12, the centering sleeve 260 includesa raised portion 268 that projects out from the proximal end 262 of thecentering sleeve body 261. The raised portion 268 defines a grip 269that can include texture such as grooves 271 and is sized and shaped tobe comfortably gripped and manipulated by a human hand. The raisedportion 268 further includes one or more flanges 270 that projectdistally from the grip 269. The flange 270 presents an inner surface 272that defines an inner diameter D16 and an outer surface 273 defining anouter diameter D17. The inner surface 272 is elongate parallel to theopposing outer surface 266 of the elongate portion 264. A gap 274 isdefined between the inner diameter D16 and the outer diameter D15. Thegap 274 is sized to slidably receive a tissue retractor 430 of avertebral implant 400 (See FIG. 2).

Referring still to FIG. 12, the retractor 430 is a substantially tubularmember and presents an inner surface 431 that defines a channel 432 andan inner diameter D18, and an outer surface 433 defining an outerdiameter D19. The inner diameter D18 is greater than the outer diameterD15 such that the channel 432 can be fit over and slidably engage withthe outer surface 266. The outer diameter D19 of the retractor 430 isless than inner diameter D16 of the flange 270, such that the retractor430 is slidably receivable within the gap 274. The retractor 430 isshaped such that it is received within the gap 274 only in apredetermined orientation.

The following is one embodiment of a method of use of the surgicalinstrument 10. Referring to FIGS. 1 and 2, a vertebral implant 400 isselected, which includes a plurality of pedicle screws 400, eachincluding a bone anchor 410 and an anchor seat 420. A retractor 430 canextend out from one or more of the pedicle screws 400. The retractor 430is releasably attached to the anchor seat 420. The bone anchor 410 isseated within the anchor seat 420 and the bone anchor 410 is thensecured to a vertebra (or other bone or surface) through drilling orscrewing. A spinal fixation rod 300 is selected from a plurality ofdifferent spinal fixation rods 300 of different sizes and shapes. Theselected spinal fixation rod 300 is engaged with the engagement assembly80 of the surgical instrument housing 11 that is in the firstconfiguration. A force F1 is applied to the biasing member 60, whichcauses the transfer assembly 150 to translate within the surgicalinstrument housing 11 until the surgical instrument 10 is in the secondconfiguration. The locking mechanism 220 engages the actuator assembly12, thereby retaining the surgical instrument 10 in the secondconfiguration.

While in the second configuration, the engagement assembly 80 preventsthe removal of the spinal fixation rod 300 from the surgical instrumenthousing 11. The spinal fixation rod 300 is pivotable with respect to thesurgical instrument housing 11 to a desired angular orientation. Anadditional force can be applied to the biasing member 60, thereby urgingthe actuator 13 and the actuation member further into the housing body181 and thus moving the surgical instrument housing 11 into the thirdconfiguration, whereby the spinal fixation rod 300 is not only unable tobe removed from the engagement assembly 80 via the application of aforce to the spinal fixation rod 300, but the spinal fixation rod 300 isalso prevented from freely pivoting within the engagement assembly 80due to the friction created through contacting members of the surgicalinstrument 10 and the spinal fixation rod 300.

A user can advance the spinal fixation rod 300 into the retractor 430 bymanipulating the grip 40. Next, the centering sleeve 260 is placed ontothe housing body 181 and then is slid along the longitudinal axis Ltoward the retractor 430 until the retractor 430 is secured within thegap 274. When positioned within the retractor 430, the centering sleeve260 centers the surgical instrument 10 with respect to the tissueretractor 430 so that the spinal fixation rod 300 can be implanted at apredetermined location relative to the vertebral implant 400. Once thecentering sleeve 260 has secured the housing body 181 to the retractor430, the spinal fixation rod 300 is properly positioned within theretractor 430. The properly positioned spinal fixation rod 300 is thensecured to the anchor seat 420, for instance by securing a locking caponto the anchor seat 420. Alternatively, the surgical system 8 can beused without the centering sleeve 260. In the absence of a centeringsleeve 260, the projection 195 (see FIGS. 5A and 5B) of the surgicalinstrument housing 11 can act as a centering spacer when the surgicalinstrument housing is placed within the tissue retractor 430 so as tocenter the surgical instrument 10 relative to the tissue retractor 430in order to implant the spinal fixation rod 300 at a predeterminedlocation relative to the vertebral implant 400. Vertebral implants suchas the vertebral implant 400 are disclosed in PCT Patent ApplicationSerial No. PCT/US2008/070670, having an international filing date ofJul. 21, 2008, the entire disclosure of which is hereby incorporated byreference as if set forth in its entirety herein. To disengage thesurgical instrument 10 from the spinal fixation rod 300, the releaseknob 231 of the locking mechanism 220 is actuated to remove the lockingshaft 221 from the actuator assembly 12 so as to disengage the actuator13.

It should be further appreciated that a surgical kit can be providedthat can include any or all of the above-described components, either asindividual components or as a plurality of differently sized components.For instance, the kit can include the surgical instrument 10 asdescribed above and a plurality of spinal fixation rods 300 that canhave different sizes or shapes or alternatively be uniform.

The embodiments described in connection with the illustrated embodimentshave been presented by way of illustration, and the present invention istherefore not intended to be limited to the disclosed embodiments.Furthermore, the structure and features of each the embodimentsdescribed above can be applied to the other embodiments describedherein, unless otherwise indicated. For instance, while variouscomponents have been described as defining diameters, it should beappreciated that the described structure need not be circular, and thusthe diameters can instead be defined by any suitably shaped crosssection as desired. Accordingly, those skilled in the art will realizethat the invention is intended to encompass all modifications andalternative arrangements included within the spirit and scope of theinvention, for instance as set forth by the appended claims.

1.-28. (canceled)
 29. A spinal fixation rod elongate along a central rodaxis, the spinal fixation rod comprising: a rod body including aproximal end and a distal end spaced from the proximal end along thecentral rod axis in a first direction; and a linkage that extends fromthe proximal end of the rod body along the central rod axis in a seconddirection that is opposite to the first direction, the linkageconfigured to couple the spinal fixation rod to a surgical instrument,wherein the linkage has an outer surface that is shaped and configuredride along a complementary shaped surface of the surgical instrument,such that when the spinal fixation rod is coupled to the surgicalinstrument the spinal fixation rod is 1) pivotable relative to thesurgical instrument through a range of rod orientations, and 2)removable from the surgical instrument only when the spinal fixation rodis in a select one of the rod orientations.
 30. The spinal fixation rodof claim 29, wherein the linkage includes a brake and at least oneengagement rail that extends out from the brake along a lateraldirection that is perpendicular to the central rod axis, the brake andthe at least one engagement rail defined by the outer surface of thelinkage.
 31. The spinal fixation rod of claim 30, wherein the at leastone is engagement rail is shaped and configured to permit removal fromspinal fixation rod from the surgical instrument in the select one ofthe rod orientations.
 32. The spinal fixation rod of claim 30, whereinthe brake is configured to engage a moveable portion of the surgicalinstrument so as to selectively inhibit the spinal fixation rod frompivoting through the range of rod orientations.
 33. The spinal fixationrod of claim 30, wherein the brake defines a curved top surface, a firstside and a second side opposed to the first side along the lateraldirection, and at least one of the first and second sides extend fromthe curved top surface to the at least one engagement rail.
 34. Thespinal fixation rod of claim 34, wherein the at least one engage rail isa first engagement rail and a second engagement rail, and the first andsecond engagement rail extend from the respective first and second sidesof the brake.
 35. The spinal fixation rod of claim 30, wherein the atleast one engagement rail includes a first engagement surface and asecond engagement surface that is angularly offset with respect to thefirst engagement surface, the first and second engagement surface extendfrom the respective side of the brake along the lateral direction. 36.The spinal fixation rod of claim 36, wherein the at least one engagementrail includes a curved third engagement surface opposed to the first andsecond engagement surfaces.
 37. The spinal fixation rod of claim 29,further comprising at least one notch that extends toward the centralrod axis where the linkage extends from the proximal end of the rodbody.
 38. A spinal fixation rod elongate along a central rod axis, thespinal fixation rod comprising: a rod body including a proximal end anda distal end spaced from the proximal end along the central rod axis ina first direction; and a linkage that extends from the proximal end ofthe rod body along the central rod axis in a second direction that isopposite to the first direction, the linkage configured to couple thespinal fixation rod to a surgical instrument, the linkage including abrake and at least one engagement rail that extends out from the brakealong a lateral direction that is perpendicular to the central rod axis,the first direction, and the second direction, the brake defining acurved top surface, a first side and a second side opposed to the firstside in the lateral direction, the first and second sides extending fromthe curved top surface to the at least one engagement rail, wherein whenthe spinal fixation rod is coupled to the surgical instrument the spinalfixation rod is pivotable relative to the surgical instrument through arange of rod orientations, and 1) the brake is configured to engage aportion of the surgical instrument so as to selectively inhibit thespinal fixation rod from pivoting through the range of rod orientations,and 2) the at least one is engagement rail configured to permit removalfrom spinal fixation rod from the surgical instrument in a select one ofthe rod orientations.
 39. The spinal fixation rod of claim 38, whereinthe at least one engagement rail includes a first engagement surface anda second engagement surface that is angularly offset with respect to thefirst engagement surface, and the first and second engagement surfacesextend from the brake along the lateral direction.
 40. The spinalfixation rod of claim 39, wherein the at least one engagement railincludes a curved third engagement surface opposed to the first andsecond engagement surfaces along a third direction that is perpendicularto the lateral direction and the central rod axis.
 41. The spinalfixation rod of claim 38, wherein the at least one engagement rail is afirst engagement rail and a second engagement rail, and the first andsecond engagement rails extend from the respective first and secondsides of the brake along the lateral direction.
 42. The spinal fixationrod of claim 38, further comprising at least one notch that extendstoward the central rod axis where the linkage extends from the proximalend of the rod body.
 43. The spinal fixation rod of claim 38, whereinthe rod body defines a cross-sectional dimension that is perpendicularto the central rod axis, the brake defines a brake length that extendsfrom the first side to the second side along the lateral direction,wherein the brake length is less than the cross-sectional dimension.